Text | "China Science News" reporter Ni Sijie
Courtesy of Zheng Zhemin Institute of Mechanics
"I came from the old era, it is my dream to make the country rich and the people strong, and I always want to do something tangible for the country, which is a very simple idea." October 2 is the centenary of the birth of Zheng Zhemin, an academician of the Chinese Academy of Sciences and the Chinese Academy of Sciences and the founder of explosive mechanics in the mainland. At a recent commemorative event, Zheng Zhemin's artificial intelligence (AI) digital human transcends time and space.
Zheng Zhemin has done many extraordinary things, but these things seem simple and natural to him. What he is best at is to extract the one that is enough to affect the whole body from the thousands of threads of others' "cutting and tidying up". And what he cares about most is how much he can do for the country.
A youth that grew up in adversity
Zheng Zhemin was born on October 2, 1924 in Jinan City, Shandong Province, the third child in the family. Because of poor health, many people say that "this child will not live long".
In September 1938, due to the war, 14-year-old Zheng Zhemin moved from Jinan to Chengdu with his father and elder brother. Because of skipping a grade after transferring to a class, lack of study, language barrier and other reasons, Zheng Zhemin suffered from a headache and was forced to suspend school.
In the fight against the disease, Zheng Zhemin slowly grew up and matured. Because of his illness, he had more time to be close to his father. Zheng Zhemin's father, Zheng Zhangfei, is a successful businessman who never follows the rules, loves to travel, cares about current affairs, respects knowledge, and regularly takes the whole family for medical check-ups.
Zheng Zhemin once recalled: "He laid a solid foundation for me in how to behave, how to learn, and how to overcome difficulties, including illness. ”
Under the careful care of his father, Zheng Zhemin, who was suspended from school, slowly improved. With his father's encouragement, he began to teach himself. One day, Zheng Zhemin found a thin original English copy of "Plane Geometry" when he was visiting a second-hand book stall and bought it. Unexpectedly, the clear logic and conclusion of the plane geometry proof aroused Zheng Zhemin's interest, and then he taught himself a book "Elementary Physics".
Because of his poor health, Zheng Zhemin has understood since he was a child that his body is the capital to do things. He has been exercising, and his body has gradually become stronger. The twists and turns of his youth have instead trained Zheng Zhemin into a "self-confident, able to live independently in school, no longer stumped by difficulties, moral awareness, pursuit of science, simple-minded, respectful of others, and low-key young man".
The birth of a new sub-discipline
On January 18, 2013, in the Great Hall of the People, 88-year-old Zheng Zhemin walked steadily onto the rostrum, received a one-and-a-half-foot bright red certificate, and became the winner of the 2012 National Highest Science and Technology Award.
The introduction of the winners reads: "Academician Zheng Zhemin is an internationally renowned mechanic, one of the founders and pioneers of explosive mechanics in mainland China, and one of the organizers and leaders of the construction and development of mechanics in China. ”
One afternoon in the early spring of 1960, a small explosion occurred in the playground of the Institute of Mechanics of the Chinese Academy of Sciences (hereinafter referred to as the Institute of Mechanics). People saw that a thin iron plate was blown into a small bowl in an instant. Qian Xuesen, then director of the Institute of Mechanics, picked up the small bowl and said meaningfully: "Don't look at it small, this is a new thing." ”
At that time, the mainland's "two bombs and one satellite" program had reached a critical period of development, and because there were no large-scale hydraulic presses in China, it was difficult to control the forming of some parts. The manufacture of nozzles and other components that are urgently needed for missiles has become a major problem for everyone. In May 1961, Qian Xuesen arranged for Zheng Zhemin and his colleagues to solve the problem of explosive formation.
Zheng Zhemin is a bachelor under the guidance of the famous mechanist Qian Weichang. At Tsinghua University, he was first exposed to modern mechanics theories such as elastic mechanics and fluid mechanics. Under the recommendation of Qian Weichang, Zheng Zhemin went to the United States to study and became a doctor under the guidance of Qian Xuesen.
Qian Xuesen often said: "There are some things in the world that seem very complicated on the surface. For those of us who do scientific work, we should have the ability to grasp the main contradictions in complex problems and analyze them, and we should focus on cultivating this ability. This experience had an important impact on Zheng's subsequent scientific career.
Qian Xuesen and Zheng Zhemin, both teachers and students, were forced to stay in United States. Before Zheng Zhemin was finally able to return to China, Qian Xuesen told him: "After returning to China, the country will do whatever it needs." Zheng Zhemin remembered this sentence for a lifetime.
When he received the task assigned by his teacher, Zheng Zhemin knew that explosive formation was a complex problem that a country urgently needed to solve. He led his colleagues to do a large number of laboratory experiments and field tests, and after some painstaking research, he studied the "explosion forming model law and forming mechanism", and cooperated with the industrial sector to apply this theory to successfully produce high-precision missile parts, making important contributions to the "two bombs and one satellite".
In 1963, Qian Xuesen named this new sub-discipline "Explosive Mechanics", and Zheng Zhemin became the leader of this discipline in the Institute of Mechanics.
An unnamed formula
Looking through Zheng Zhemin's academic contributions, we can see that he has done a lot of great things, and has made outstanding work in many fields such as fluid elastoplastic body modeling, armor piercing theory, explosion processing, engineering blasting, gas outburst, and landslide disaster prevention.
"His scholarly contributions can be represented by a mathematical formula – ρV2/σY." Ding Yansheng, a student of Zheng Zhemin and one of the authors of "The Biography of Zheng Zhemin", said in an interview with China Science News.
"ρV2/σY" is a landmark formula in explosion mechanics, and Zheng Zhemin is an important discoverer. This formula characterizes the mechanical behavior of matter under the action of impact force, can accurately predict the pressure decay law of underground nuclear test, and has contributed to the prediction of the yield of the first underground nuclear explosion in the mainland.
Regarding this formula, Bai Yilong, a student of Zheng Zhemin and an academician of the Chinese Academy of Sciences, once wrote: "The common saying is that it is called the number of damages, which is the result of the United Kingdom scholar W. Johnson made it official in 1973. However, some people, such as Mr. Tan Qingming from the Institute of Mechanics, have disputed this in the conversation, pointing out that Mr. Zheng Zhemin discovered and used this dimensionless number ...... earlier."
In June 2021, two months before Zheng Zhemin's death, Bai Yilong, who was also hospitalized in Peking University Hospital, asked Zheng Zhemin to verify that dusty history.
At that time, Bai Yilong recounted his understanding of the process of discovering this formula: "I've been thinking about it for the past few days, I guess so, I'll say, are you right?" To do nuclear explosion wave attenuation, we must use the energy equation, so that the kinetic energy per unit volume will come out, and the work done by stress will be decomposed into volume deformation and shear, and the shear-related yield stress will also come out, and this dimensionless number will naturally come out, leaving only the volume deformation effect. ”
After listening, Zheng Zhemin nodded: "Yes." It's natural. ”
"In terms of time, a nuclear explosion should be done before you go to the 'May Seven' school." Bai Yilong continued.
"Well, yes. That should have been between '65 and '68. At the time, it wasn't given a name, or anything. Zheng Zhemin replied softly.
This conversation was recorded in text by Bai Yilong, and then included in "The Biography of Zheng Zhemin". Bai Yilong wrote: "I hope that this small article can leave a concrete, historically true, and scientific history record for future generations of scholars to refer to." ”
Zheng Zhemin did not think of naming the formula, or naming the formula after his own name according to international practice. Perhaps, more concerned than these things, he is more concerned about the happiness of doing scientific research.
He once said: "In the face of a scientific research problem, the most important thing is to first clarify the problem, which is often the most important and laborious, and it is easy to be ignored." The core is to find the main contradiction that solves this problem. This often requires different attempts and multiple failures, so patience and persistence are required. One day, you will feel that all of a sudden there is a connection, that the factors that used to be disconnected become logically connected, and that you are sure that you have found the answer to your question. This is the happiest moment for doing scientific research. ”
Ding Yansheng sighed: "He (Zheng Zhemin) is good at grasping the essence and key from complex phenomena, establishing simplified models, explaining basic laws, and then applying laws to truly solve practical problems in combination with typical situations of engineering or process." ”
Some experiences that have been handed down
In January 2013, when he won the country's highest science and technology award, Zheng Zhemin said with trepidation: "At such an age, how much can I do for the country, I always feel as if I owe something." ”
Until he was 95 years old, he would still think, "I really didn't expect that I would live to this day." Now that we have this God-given opportunity, we can't help but ask, what do we have to leave for future generations? What experiences do you want to share with future generations? What advice do you want to leave for those who come after you? ”
He strives to pass the baton of technological development to the future.
Ding Xiaoliang, a doctoral student who graduated in 1988, remembers that he became interested in management during his degree, and participated in the management of the canteen food management committee of the Institute of Mechanics in addition to carrying out research on coal and gas outburst under the supervision of Zheng Zhemin. After Zheng Zhemin found out, he did not blame him for not devoting himself to scientific research. "He is very open-minded and encourages young people to develop according to their aspirations." Ding Xiaoliang said.
Gao Jianbo, a master's student who graduated in 1991, often remembers what Zheng Zhemin told him: "100% faith, and at the same time 120% doubt." "Faith" is the belief in the importance and foresight of one's chosen field and issue; "Skepticism" is questioning knowledge in a chosen field, where even the most basic things can be wrong.
Wang Yi, a doctoral student who graduated in 2010, also had an unforgettable conversation in his heart. At that time, Zheng Zhemin reviewed his dissertation and asked him, "Why do you want to adopt such dimensionless parameters?" Wang Yi replied: "The papers of experts in this field all use this set of dimensionless parameters, so I also use them." Zheng Zhemin asked rhetorically: "Everyone else uses it like this, is it necessarily okay?" Do you have to use it along? Later, under the guidance of Zheng Zhemin, Wang Yi adopted new parameters, and the conclusions of the paper became simpler and clearer.
In August 2021, Zheng Zhemin passed away at the age of 97. Time can't take away thoughts, and to this day, many people still have tears in their eyes when they talk about Zheng Zhemin.
At the commemoration of Zheng Zhemin's 100th birthday, his AI digital human once again shared his experience with future generations across time and space: "If you ask me, what is the most important thing? I would answer that learning to be a human being is the most important thing. Be honest, trustworthy, do not do to others what you do not want to do to others, be lenient with others and strict with yourself, and do not talk about others behind your back; We should treat our work with a clear distinction between public and private, seek truth from facts, be conscientious, keep improving, re-promise, and rely on ourselves first if we have difficulties. These are the words I want to leave for posterity. ”